After some more checks it seems the issue is caused by ssim x86 assembly. When running the command with "-cpuflags 0" it disappears.

Further the issue seems to be unrelated to rgb24 pixel format, when running the command in Valgrind both rgb24 and yuv422p formats cause errors to be printed. I'm attaching the log files generated with Valgrind for rgb24 and yuv422p.